Some specific aspects of cell-surface recognition by sipunculid coelomocytes.

Sipunculid worms have been the subject of research on the phylogeny of immune responses since the investigations of Cantacuzene (1). These marine worms comprise a distinctive group that inhabit intertidal areas scattered over the world. While a variety of discoveries has been made in sipunculids that are of immunological interest, emphasis is made that no specific molecular or cellular reactions have been found in this phylum that are comparable to those of vertebrate adaptive immunity. The discoveries that have been made include the phagocytic and encapsulation reactions common to invertebrates, the occurrence in some species of specialized free-swimming phagocytic structures in coelomic fluid termed “urns” (1), an inducible lysin for a protozoan (2), inducible and noninducible bactericidins (3, 4, 5), a capacity to hemolize (6, 7) and agglutinate vertebrate erythrocytes (8), an agent capable of immobilizing dinoflagellates (6), substances with specificities related to vertebrate blood groups (9) and an inhibitory effect on phagocytosis by bovine serum (10).